The present applicant previously proposed a floor cleaning sheet characterized by being impregnated with 100 to 1000% by weight, based on the sheet weight, of an aqueous detergent having a viscosity of 20 to 30000 mPa·s at 25° C. (see JP-A-2001-198065). The floor cleaning sheet is typically attached to a mop-like cleaning tool on use. With this floor cleaning sheet, the aqueous detergent is slowly released in a stable manner, and a wide area can be cleaned with good operationality (ease of use). However, the floor cleaning sheet is mainly contemplated to be used to wipe off light dust and dirt, such as hairs, soil dust, and dried soy sauce stains, from flooring. Accordingly, the amount of the detergent the sheet is designed to release per tatami (“tatami” is a 90 cm wide and 180 cm long mat and is used to mean an equivalent area) is as small as 1.6 g or less for first tatami and 0.6 g or less for second to nth tatami. In other words, what is aimed at is very slow release of a detergent. Such a small amount of the released detergent may not be seen as enough to remove heavy persistent stains. That amount can be seen as insufficient particularly in applying a polish. At least about 2 g of a polish should be released per tatami stably in order to give a uniform spread of the polish to flooring. Besides, in applying such an agent as a polish, the sheet should have a liquid impermeable layer on its side to be brought into contact with a mop-like cleaning tool, to which it is attached, so that the cleaning tool may not be soiled.
The present applicant also proposed a detergent-impregnated article (sheet) comprising a detergent retentive layer containing a hydrophobic material and a pair of detergent releasing layers that are denser than the detergent retentive layer, the detergent retentive layer being held in between the detergent releasing layers (see JP-A-10-272082). The main subject to which the article is intended to be applied is glass, and the article is designed to be hand held. Furthermore, the article is characterized in that the release of the detergent is regulated by folding the sheet. Accordingly, the article is not optimally designed to be attached to a tool and to slowly release a detergent from only one side thereof, which is not folded back, to a wide area such as flooring.
The present applicant also proposed a cleaning sheet comprising a wiping part and a liquid absorbent member which absorbs the liquid wiped up with the wiping part, the wiping part being a liquid permeable surface sheet having a large number of projections (see JP-A-9-131288). The proposed cleaning sheet itself is not impregnated with a detergent. It is used to carry out cleaning while wiping up a detergent separately supplied to a surface to be cleaned.
Apart from these cleaning sheets, JP-U-4-33971 discloses a disposable applicator comprising a resin film bag with a joint a part of which is adapted to be opened under applied pressure, a liquid to pasty agent sealed into the bag, an agent-impregnated layer disposed on one side of the bag, an agent permeation controlling layer provided on the agent-impregnated layer, an agent-permeable wiping layer provided on the agent permeation controlling layer, and an agent-impermeable layer disposed on the other side of the bag, all these members being joined together. The resin film bag with a joint a part of which is adapted to be opened under pressure may be replaced with a resin film bag with holes which are sealed with an adhesive film. Since the resin film bag of the applicator is adapted to be opened under pressure, there is a fear that the bag is unintentionally opened under some pressure applied during preparation, transportation or storage, resulting in leakage of the agent. The applicator is not designed to be best suited for slow release of a polish, etc. in treating a wide area such as flooring, nor for attachment to a cleaning tool.
An applicator comprising an agent container having an agent sealed therein, a sealing member attached to the agent container and capable of forming holes in the agent container when removed, and a wiping layer provided on the sealing member is also known (see JP-A-10-127549 and JP-A-10-262889). In view of the drawback of the applicator of JP-U-4-33971 supra that the openable film bag containing an agent is likely to be opened unintentionally by pressure application during preparation, transportation or storage to leak the agent, the above-described applicator is characterized by eliminating such a trouble. According to the publication, where the individual holes formed by removing the sealing member have an area of 1 mm2 or less, and the total opening area is 0.002 to 0.02% of one side area of the container, the applicator releases the agent slowly to have an extended service life, supplying the agent uniformly from beginning to end of application. However, where the individual holes are as small as 1 mm2 or less, and the total opening area ratio to the area of one side of the container is 0.002 to 0.02%, the applicator is incapable of uniformly releasing a large amount of an agent over a wide area to be treated.
Accordingly, an object of the present invention is to provide a wet cleaning sheet capable of releasing a large amount of a detergent or a polish uniformly from the beginning to the end of cleaning to a wide area to be cleaned such as a floor.